Overlapping operations in material requirements planning

Material requirements planning (MRP) is a planning and information system that has widespread application in discrete-parts manufacturing. The purpose of this article is to introduce ideas that can improve the flow of material through complex manufacturing systems operating under MRP, and that can increase the applicability of MRP within diverse manufacturing environments.MRP models the flow of material by assuming that items flow from work station to work station in the same batches that are used in production. That is, once work starts on a batch of a certain item at a certain work station, the entire batch will be produced before any part of the batch will be transported to the next work station on its routing plan. Clearly, efficiency can be increased if some parallelism can be introduced. The form of parallelism investigated here is overlapping operations.Overlapping operations occurs when the transportation of partial batches to a downstream work station is allowed while work proceeds to complete the batch at the upstream work station. The potential efficiencies to be gained are the following:

• Reduced work-in-process inventory

• Reduced floor space requirements

• Reduced size of transfer vehicles

Additional costs may accrue through additional cost of transportation of partial batches and through additional costs of control.Some MRP software vendors provide the data processing capability for overlapping operations. However, the user is given little or no guidance on overlapping percentages or amounts. It is our intent to provide a simple, robust technique to MRP users who would like to overlap operations and gain some or all of the above efficiencies.An optimal lot-sizing technique is derived by considering a generic two work station segment of a manufacturing system. Under the assumptions of constant demand and identical production rates, a cost function that considers setup costs, inventory holding costs and transportation costs is derived. This cost function is minimized subject to the constraint that the production batch is an integer multiple of the transfer batch. We solve for the optimal production batch, the optimal transfer batch, and the integer number relating them. Solutions are obtained as closed form, easy to-evaluate formulas.By introducing more parallelism, overlapping operations can reduce lead time. However, this will not happen without modification of MRP logic to accommodate such reduced lead time. We derive a formula that shows how a significant lead time compression can easily be obtained and implemented in MRP.We consider an example to illustrate the application of the technique on typical data from the electronics industry. The outcome showed a cost savings of approximately 22.5% over the standard MRP approach.Overlapping operations allows the applicability of MRP to an increasing number of situations that are not modeled faithfully by conventional MRP logic. Three such situations that occur often are the following:

• Limited size of transfer vehicles dictate that several transfers should be planned.

• Lead time requirements prohibit nonoverlapped operations.

Our analysis suggests how to accommodate these difficult practical situations into MRP.Overlapping operations in material requirements planning provides an enhancement that allows wider applicability, shortened lead times, and lower total costs. It may be applied selectively to any two work stations where it is deemed appropriate. Due to the structure of the cost function, it is possible to make the transfer lot-sizing decisions independent of the production lot-sizing decisions. Therefore, significant improvements can be made through overlapping with minimum disruption to the existing MRP system machinery. It is our conviction that overlapping operations is an important concept that can and will impact MRP. We suggest the approach presented here as a systematic way to implement overlapping.     

Employees' experience of human resource practices under plural form franchising: The impact of front-line managerial capability

The franchising business model has received scant attention within the field of human resource management (HRM). Data tracking workers' experience of this format are more elusive still. This study draws on comparative, qualitative data derived from discussions with 82 respondents working within the corporate and franchised divisions of a market leading, fast food multinational company (MNC). Extant analyses of franchised operations point to shortcomings in franchisees' treatment of staff. This outcome is typically asserted to be the result of the opportunism that flows from the desire to maximise revenues and minimise costs. This emphasis on structural pressures ignores the micro-level influences and the complexity of the day-to-day dynamics of the employment relationship. Specifically, the impact of the leadership skills and competence of front-line managers (FLMs) is overlooked. The study highlights that differences in FLM capability significantly affect the work climate, further aggravating poor HR activities in the franchised units, while offsetting some of the repressive task features associated with routinised work in the corporate division.     

TECHNOLOGY AND SPAN OF CONTROL: WOODWARD REVISITED

This study of production operations in 95 New Jersey manufacturing firms explains the widely replicated curvilinear relationship between first line supervisory span of control and Woodward's technological complexity scale. Revisiting Woodward led to the initial proposition that the relationship was a by-product of the differing degree of task variability among the major types of production operations. A subsequent literature review of administrative requirements suggested the importance of size, complexity and automaticity on supervisory span of control. Our data indicate that variations in the span of control of production operations classified according to Woodward's scale are attributable to the underlying effects of size and task complexity. Technology, whether operationalized as Woodward's production types or automaticity of machinery explained little variation in the span of control of first line supervisors.     

Benefits and barriers of telework: perception differences of human resources managers according to company's operations strategy

Telework as an integration of Information and Telecommunication Technologies with Human Resources management, means a new job organisation paradigm for companies working in the New Economy. However there are very few empirical studies that have analysed the perception differences of telework benefits and barriers in industrial and service companies. This paper contributes with empirical data to the relationship between the use of telework techniques and the implementation of this new work organisation with the company's operations strategy. The paper uses data from Spanish companies to test the relationship between innovation, employee training, and other production strategy performance parameters with the feasibility of telework adoption.     

The long-run relationship between private and public savings: An empirical note

This empirical note extends the recent work by Holmes (2006) in examining the long-run relationship between private and public savings in the U.S. over the post-World War II period. Standard Engle-Granger cointegration tests fail to reject the null hypothesis of no cointegration; however, once allowance is made for an endogenous break in the cointegrating relationship, the weak form of the Ricardian equivalence proposition is supported.     

大型钢铁企业组织结构的规模效率分析

首先,分析了我国钢铁行业发展的特点,认为产品结构不够完善、行业集中度较低以及企业规模偏小是我国钢铁企业面临的主要问题,而规模是造成上述现状的根本原因;国际钢铁业已进入由大企业集团主宰的国际市场化阶段,我国钢铁企业需要扩大规模,增加在国际竞争中的话语权。其次。围绕企业的规模运作,运用经济学模型对产业链的大规模企业生产模式进行了分析,从理论视角论证了企业扩大规模的动机以及规模优势产生的机制和所需条件。大型组织结构优势产生的机制在于,通过生产及运营要素的优化整合实现合理分工协作,从而降低运营成本,提高企业的竞争力。此外,对钢铁企业采用的组织结构特点和运营模式进行了探讨,一元式的组织结构能够发挥职能分工所带来的效率,然而高度的集权特征不适用于超大规模企业的管理决策。控股公司和事业部结构体现了规模化后组织结构由集权向分权转化的趋势,但在运行中面临的效率障碍在于无法消除部门机会主义．分权后权威统筹机构的缺位以及传统的规模企业应当分权的逻辑需要企业重新思考。在上述分析基础上提出．钢铁企业在实现形式上的规模化后,需要考虑技术任务特征、信息处理以及权力的分化整合之间的平衡,构造合理的控制机制以保证规模优势的实现。     

Linking performance drivers in production planning and inventory control to process choice

This study investigates how process choice relates to production planning and inventory control decisions. We empirically examine the validity of deductively derived patterns about these types of decisions. More importantly, we look for normative insights by exploring how production planning and inventory control decisions affect operations performance. Our findings show that production line and continuous flow plants use more of a level production strategy, and carry less raw material and work-in-process inventory. The performance drivers for these plants, through which the operations function excels, are effective utilization of equipment, reduced finished goods inventory, and reduced setup down time. To gain forward demand visibility and batching economies, job and batch shops rely much more on backlogs in their planning process. These plants use more of a production chase strategy and position inventory lower in the bills of materials. Four performance drivers for top-performing job and batch shops are to find ways that better anticipate customers' orders, have a more responsive chase strategy, carry less raw material or purchased inventory, and shorten production planning horizon, partly through less reliance on backlogs. It is intriguing that top-performing plants not only do the expected things, given their choice of process, but also excel in selected dimensions—some of which fit the profile normally associated with a different process choice. To monitor and continuously improve operations, evaluation ‘scorecards’ should pay particular attention to performance drivers, which change depending on the plant's process choice.     

Professional Competence as Ways of Being: An Existential Ontological Perspective

Current theories propose that professional competence is primarily constituted by scientific and tacit knowledge, knowing-in-action, understanding of work or practice. While providing valuable insights we contend that they present a fragmented understanding of professional competence. In particular, they do not adequately explain how central aspects of practice such as knowledge and understanding are integrated into a specific professional competence in work performance. An existential ontological perspective is proposed as offering a more comprehensive and integrative analysis of professional competence. It is explored through an empirical study of corporate lawyers and the findings suggest that professional competence should be understood as ways of being. The results show that different ways of practising corporate law distinguish and integrate a specific understanding of work, a particular self-understanding, other people, and tools into distinct forms of competence in corporate law.     

Taking charge and employee outcomes: the moderating effect of emotional competence

This study examined how taking charge was related to job satisfaction, affective organizational commitment, and job performance among Hong Kong Chinese newcomers, and how emotional competence moderates the latter relationships. The results of a two-wave survey involving 137 newcomers supported the proposition that taking charge would be positively associated with job satisfaction and affective organizational commitment, but not with job performance. In addition, emotional competence significantly moderated the relationship between taking charge and job performance, such that taking charge was positively related to job performance only when newcomers’ emotional competence was high.     

Beyond improved quality: the motivational effects of statistical process control

The deployment of statistical process control (SPC) in manufacturing environments is a prominent global phenomenon. Managers have frequently justified investments in SPC by citing and/or demonstrating the improvements in quality and costs from the effective implementation and practice of SPC. This paper complements this rationalization by presenting conceptual arguments and empirical evidence to further our understanding of the motivational effects that result from the deployment of SPC within production environments. Several hypotheses derived from relating the deployment of SPC to process operators’ jobs and their affective reactions to work are tested using data provided by 100 process operators. The empirical results, generated from applying path analysis, suggest that the effective implementation and practice of SPC, in fact, would create more enriched jobs for process operators that lead to higher levels of work motivation and job satisfaction.     

A meta-analysis model of manufacturing capabilities

Recent research in operations strategy has focused on showing the extent to which manufacturing's competence in developing and executing one or more competitive capabilities affects the organization's overall business performance. Several of those efforts have produced models, such as the ‘sand cone’, that suggest an ideal sequence in which manufacturing capabilities should be developed. However, efforts to empirically validate such sequential models, except for one recent study, have been inconclusive. This paper takes a different approach to examining the relationships among competitive capabilities. The existing cross-sectional studies of manufacturing capabilities are integrated to synthesize a proposed model of: (1) the relationships among manufacturing capabilities, and (2) the relationships between those capabilities and business performance. The proposed model is synthesized using data from previous studies, other models and theoretical arguments. Meta-analysis is used to identify aspects of the model that appear better supported by empirical research and those that require further study. The implications of this proposed model with regard to research, practice and future research in operations strategy are discussed.     

Wages,Prices and Politics: Evidence from Norway

This paper studies the empirical relevance of the close ties between a central trade union and the social democratic political party using time series data for Norway. Using a structural wage-price model we estimate that changing from a bourgeois to a social democratic government reduces manufacturing wages in the long run by 2.3 percent. This result is consistent with a wage bargaining model augmented by political preferences of the union leaders. Private service wages are not directly affected by government type, but wage spillover effects imply that the long-run dampening effect in the private service sector is around 2 percent. The results also support the proposition of the Scandinavian model of inflation that the traded goods sector is the wage leader.     

Supply chain integration and operational performance: The contingency effects of production systems

The boundary conditions of supply chain integration (SCI) have been widely studied in order to find out when SCI is applicable and effective. However, prior studies have mainly focused on external contextual factors, such as supply complexity, environmental uncertainty and country-level infrastructure. This study contributes to the SCI literature by examining the contingency effects of internal production systems on the relationship between supplier integration, customer integration and operational performance. Based on organizational information processing theory, we provide evidence to show that the impact of supplier and customer integration on operational performance varies across production systems, such as one-of-a-kind production, batch production and mass production systems. The empirical results also reveal how supplier and customer integration can be matched with different configurations of production systems in order to achieve the desired quality, flexibility, delivery or cost performance.     

Cross-entropy estimation in technical efficiency analysis

Technical efficiency analysis is a fundamental tool to measure the performance of production activity. Recently, an increasing interest in the state-contingent approach has emerged in the literature although such interest has not yet been accompanied by an increase of empirical applications. This is largely due to the fact that empirical models with state-contingent production frontiers are usually ill-posed. In this work, a discussion on the role of the generalized cross-entropy estimator within the state-contingent production framework is presented. To the best of the authors’ knowledge, the example provided in this work is the first real-world empirical application on technical efficiency analysis with the state-contingent approach using the generalized cross-entropy estimator.     

Statistical Approaches for Non‐parametric Frontier Models: A Guided Tour

A rich theory of production and analysis of productive efficiency has developed since the pioneering work by Tjalling C. Koopmans and Gerard Debreu. Michael J. Farrell published the first empirical study, and it appeared in a statistical journal (Journal of the Royal Statistical Society), even though the article provided no statistical theory. The literature in econometrics, management sciences, operations research and mathematical statistics has since been enriched by hundreds of papers trying to develop or implement new tools for analysing productivity and efficiency of firms. Both parametric and non‐parametric approaches have been proposed. The mathematical challenge is to derive estimators of production, cost, revenue or profit frontiers, which represent, in the case of production frontiers, the optimal loci of combinations of inputs (like labour, energy and capital) and outputs (the products or services produced by the firms). Optimality is defined in terms of various economic considerations. Then the efficiency of a particular unit is measured by its distance to the estimated frontier. The statistical problem can be viewed as the problem of estimating the support of a multivariate random variable, subject to some shape constraints, in multiple dimensions. These techniques are applied in thousands of papers in the economic and business literature. This ‘guided tour’ reviews the development of various non‐parametric approaches since the early work of Farrell. Remaining challenges and open issues in this challenging arena are also described. © 2014 The Authors. International Statistical Review © 2014 International Statistical Institute     

Offshoring knowledge and service work: A conceptual model and research agenda

This paper presents two complementary conceptual models that help shed light on the complexities of offshoring service and knowledge work. In developing the model, we draw upon existing literature in the realm of service operations and delivery and build on insights from allied areas such as management and practice. The models offer a simple yet powerful way to conceptualize offshoring of knowledge and service work and to identify the inherent challenges that such strategies entail. The evolutionary model of offshoring parallels well-established work in the manufacturing literature to present a sequential view of building organizational competence in offshoring. The implications of the conceptual models have been discussed in a range of propositions that can be viewed as foundations for new inquiry in this research stream.     

Capital-tax financing and scale economies in public-input production

Contrary to the dominant view of inefficient tax competition, Oates and Schwab (1991) show that capital-tax financing of public inputs leads to efficiency when the supply of these inputs is conditioned on business investment (Oates, W.E., Schwab, R.M., 1991. The allocative and distributive implications of local fiscal competition). This paper demonstrates that the cost structure of public-input production is relevant to their proposition on efficient capital-tax financing. That proposition holds if the per-unit cost of public inputs is exogenously fixed; however, it does not hold if public-input production exhibits scale economies. Also, this paper compares our analysis with the Zodrow-Mieszkowski model. That comparison illustrates the importance of the way public inputs are rationed to private firms.     

The relationship between the level and variability of inflation: Theory and evidence

This paper emphasizes the role played by asymmetric stabilization policies in producing the widely reported positive association between the level and variability of inflation. A simple theoretical model is constructed which shows how asymmetric policies give rise to this association. The empirical findings presented provide support to the proposition that variations in inflation uncertainty are policy-induced.     

Intra-organizational impediments to the development of shopfloor competence and commitment: The case of a Finnish-owned greenfield paper mill in East Germany

Building new production facilities abroad poses a huge challenge to the human resource practices of a firm. This is because reaching the required level of competence and commitment is not possible without adjusting these practices to the characteristics of local personnel. However, there are few empirical studies that highlight how such situations have actually been handled. This paper makes a contribution through an examination of the initial phases of a Finnish-owned greenfield paper mill in East Germany. The evidence used in the study includes documentary analysis, interviews and discussions with actors at the different organizational levels. The case study demonstrates how managerial subdivisions and the absence of local actors from the higher levels of the managerial hierarchy impede development of competence and commitment among the new employees. The evidence presented suggests that the involvement of various organizational actors in human resource management processes should be given more weight in further research.     

Cell生产方式在电视机生产中的应用

单元式(Cell)生产作为一种与传统流水线式生产截然不同的生产组织模式,在应对多品种、小批量、短交期的订单方面有着独特的作用。它基于精益生产的原则,进行灵活布局,由单个工人进行多任务操作,进行单件制造,消除传统流水线中存在的等待、搬运、WIP等浪费,提高生产效率。本研究中,通过在电视机生产中引入Cell生产模式,以满足多品种小批量订单需求。